This application is a request for continuation of support for a predoctoral training program in Microbial pathogenesis at Yale University. The goal of this program is to train students in multidisciplinary approaches to the study of microbial pathogenesis. The training faculty shares the view that the understanding of the biology of pathogenic microorganisms requires experimental approaches and concepts from different fields of science. Therefore the program seeks to provide students with the necessary broad experimental skills and knowledge that will allow them to pursue a future research career in the study of microbial pathogens. The existence of very strong basic science departments committed to this concept coupled to the recent launching of the Section of Microbial Pathogenesis at the Yale School of Medicine creates a unique environment in which this training program can flourish and produce superbly trained scientists. The training program consists of formal course work and laboratory rotations during the first two years. This provides a solid and broad conceptual foundation and knowledge base as well as broad experimental training through the laboratory rotations. Students select a research advisor during the second year and prepare and defend a research proposal that will serve as the foundation for the dissertation research project. A Thesis committee monitors the student progress throughout the thesis research process and, finally, the preparation of the dissertation. Students enter the program through the Combined Program in Biological and Biomedical Sciences (BBS). The BBS unites the more than 200 faculty in basic biological and biomedical sciences at the Yale Medical School and Science Hill on the main University Campus. Admission is granted to students with outstanding academic record with particular attention to research experience. The training Faculty hold primary appointments in different basic science as well as clinical Departments and carry out research in a broad range of topics that are directly relevant to microbial pathogenesis. This breath gives student unique opportunities to explore different aspects of microbial pathogenesis research. Trainees are also provided with multiple opportunities for scientific interactions not only within the home Department but throughout Yale University.